HAM Annuity Calculator

1 Project Master

Package Code

Project Name

Region (price-variation basis)

Bid Project Cost (Rs)

Quoted First Year O&M (Rs)

Bid Due Date

Appointed Date

PCOD (5th milestone / 90%)

COD (6th milestone / 100%)

Base Price Indices (as on Reference Index Date preceding Bid Date)

Base CPI (Base 2001=100)

CPI Weight

Base WPI (Base 2011-12=100)

WPI Weight

Inflation Factor = ROUND( (CPI×w_CPI + WPI×w_WPI) ÷ (BaseCPI×w_CPI + BaseWPI×w_WPI), 2 ). CPI/WPI of the previous month of each IE report date is used.

Change of Scope (COS) & Length Revision

COS Amount (Rs)

COS Sign

Positive COS Treatment

Revised BPC (RBPC) (Rs)

Length Factor (new ÷ original length)

Effective First Year O&M (Rs)

Per requirement: if COS exists, BPC is revised unless a positive COS is paid directly. If project length changes, First Year O&M is revised proportionately by the Length Factor.

Extension of Time (EOT) & CPI/WPI Freeze

Delay beyond Appointed + 730 days

Second EOT last date

Freeze CPI/WPI projection at Second EOT date

If the project is delayed beyond 730 days, EOT is required. When freeze is enabled, the projected O&M inflation factor is frozen at the Second EOT date. Construction milestone CPI/WPI are entered as certified by the division.

2 Bank Rate History & Index Data

Effective From	Bank Rate (%)	Repo (%) ref	Remark

Interest margin over Bank RateArticle 23.6.4: Bank Rate + 3%

Interest method

Latest All-Commodities WPI (ref)RBI/OEA seeded

Latest CPI (ref)Centrewise seeded

3 Star Rate Components (Konkan CSD)

For Konkan PWD projects the price variation of cement, steel and bitumen is computed on star rates (not CPI/WPI). The remaining share of BPC follows CPI/WPI. Enter each material's share of BPC and its base star rate; enter the milestone-wise star rate inside the construction table.

Material	Share of BPC (weight)	Base Star Rate

Inflation Factor (Konkan) = ROUND( Σ w_m×(StarRate_m ÷ BaseStarRate_m) + (1 − Σw_m)×CPIWPI-multiple, 2 ).

4 Construction Milestones — Completion Cost (Annexure 2)

Milestone	IE Report Date	CPI	WPI	Cement SR	Steel SR	Bitumen SR	Cum. Progress %	Const. Support %	Amount Paid in Construction (Rs)

Milestone V date auto-links to PCOD, Milestone VI to COD. Amount Paid = actual certified BPC disbursement during construction (used to derive the outstanding balance annuitised over the operation period).

5 Annuity & O&M Schedule (Operation Period)

Number of biannual installments

First annuity offset from COD (days)180th day of COD (+2 grace)

O&M projection escalation (p.a.)for future installments

GST on O&M

GST on Interest

GST rate on Interest

Edit the Annuity % and O&M % per installment (they mirror the Article 23.6.3 schedule). For any installment where the actual IE-certified CPI/WPI is available, enter it to override the projection.

No	Fiscal Year	Annuity %	O&M %	Actual CPI (opt.)	Actual WPI (opt.)

Static single-page calculator · host at HAMAnnuityCalculator.sspca.in. To enable live "Fetch latest", deploy a small serverless proxy (e.g. Cloudflare Worker / Vercel function) that fetches RBI Bank Rate and OEA WPI and returns JSON with an Access-Control-Allow-Origin header, then set PROXY_URL in the script.

1 Project Master

2 Bank Rate History & Index Data

3 Star Rate Components (Konkan CSD)

4 Construction Milestones — Completion Cost (Annexure 2)

5 Annuity & O&M Schedule (Operation Period)

Summary — First Annuity & O&M payable

Annexure I — First Annuity & O&M Amount

Annexure II-A — Completion Cost Working

Annexure II-B — Annuity & O&M Working (all installments)

Yearwise Summary of Payments